Conventional electrophotographic apparatus, such as copiers, printers, facsimile machines, etc., comprise an image bearing member, such as a photoconductive element, normally in the form of a drum or belt. Arranged in timed sequence around the image bearing member are a plurality of processing stations for performing various functions. These processing stations may comprise stations for charging the image bearing member, imagewise exposing the charged image bearing member to electrostatically form a latent image thereon, developing the latent electrostatic image with a developer commonly referred to as toner, transferring the toner developed image from the image bearing member to a substrate, such as paper, cleaning the image bearing member, i.e., removing residual toner and other contaminants from the surface of the image bearing member, and fixing the transferred toner developed image on the paper.
A typical reproduction operation comprises charging the image bearing member, such as a photoconductive drum, and exposing the charged surface to a light pattern of an original image to be reproduced, thereby selectively discharging the surface in accordance with the original image. The resulting pattern of charged and discharged areas on the surface of the photoconductive drum forms an electrostatic charge pattern or electrostatic latent image conforming to the original image.
The latent electrostatic image is developed by contacting it with finely divided toner which is held by electrostatic force on the image bearing member. The toner image is transferred to a substrate, such as paper, in a transferring device into which paper is fed by a registration roller toward the drum in synchronization with drum rotation. As the leading edge of the paper abuts the drum, electrostatic forces adhere the two together, and the transferring device transfers a toner image from the photoconductive drum to the paper. After transfer, the toner image is fixed to form a permanent record.
Subsequent to development, and after transfer of the developed image to the paper, some toner inevitably remains on the photoconductive drum, held thereto by electrostatic and/or Van der Wals forces. Additionally, other contaminants, such as dust, paper fibers, toner additives, Kaolins and various other forms of debris, have a tendency to be attracted to the charge retentive surface.
Contemporary commercial automatic copiers/reproduction machines, optical printers and facsimile machines comprise an electrostatographic image bearing member, which may be in the form of a drum or belt. The image bearing member moves at high rates in timed unison relative to a plurality of processing stations. This rapid movement of the electrostatographic image bearing member requires vast amounts of toner to be employed during development. Associated with the increased amounts of toner is the difficulty in removing residual toner remaining on the image bearing member subsequent to transfer.
One type of device conventionally employed for charging the image bearing member is a corona charger normally positioned slightly spaced apart from the surface of the image bearing member for applying a surface charge thereto. However, corona chargers are known to exhibit disadvantages, such as low charging efficiency, ozone generation, image blurring and high maintenance requirements. The disadvantages associated with corona chargers have led to the implementation of alternatives, such as a contact type charge inducing member, notable a charging roller, which is maintained in contact with the surface of an image bearing member, e.g., a photoconductive drum. The charging roller charges the photoconductive drum by contact while a voltage is applied to the charging roller, thereby charging the photoconductive drum at an advantageously relatively low voltage. Since a discharge is not established, ozone is not generated and the accumulation of dust on the wire electrode of a typical corona charger is avoided.
During operation, toner and other contaminants, including airborne particles, inevitably accumulate on the charging member, as from the surface of the photoconductive drum, particularly as the number of imaging cycles increases, thereby decreasing its charge inducing efficiency. In addition, toner and other contaminants, such as dust, tend to redeposit on the photoconductive drum, resulting in poor quality reproductions.
A prior attempt to address charging roller contamination is disclosed in Japanese Utility Model No. 58-81538, wherein toner and other contaminants are removed from the surface of a charging roller by contact with a fur-brush. Another prior approach is disclosed in Japanese Laid Open Patent No. 03-100676, wherein toner and other contaminants are removed from a charging roller with a foamed urethane sponge. In Japanese Laid Open Patent No. 02-301779, toner and other contaminants are removed by a cleaning member in the form of a web, such as a cloth web. These prior cleaning attempts have proved to be less than satisfactory.
The prior technique of removing toner and other contaminants from a surface of a charging roller by scraping with a fur-brush requires frequent periodic disposal of removed material, which is a time consuming and dirty manual operation. A receptacle is positioned remote from the image bearing member to accommodate removed material. However, it is necessary to remove the receptacle to dispose of the removed material at frequent intervals, which is manifestly costly and inefficient. The use of a sponge cleaning member also lacks efficiency due to its limited collection capacity which is reached quickly in normal operation. Therefore, an operator is required to exchange sponge cleaning members at frequent intervals. Cloth web cleaning members are also inefficient, since removed toner and other contaminants remain on the web causing gradual deterioration. Cloth web cleaning members also become impractical with large image forming apparatuses.
In a conventional image forming apparatus, a substrate, such as a sheet of paper, is fed to a transferring station wherein the toner developed image is transferred from the image bearing member to the paper, typically by means of a transferring roller. During operation, the surface of the transferring roller also becomes contaminated with toner and other particulate contaminants, thereby deteriorating the quality of the transferred image.